This invention relates generally to the field of hard disc drive data storage devices, and more particularly, but not by way of limitation, to rotational movement of disc drive actuators.
Disc drives of the type known as xe2x80x9cWinchesterxe2x80x9d disc drives, or hard disc drives, are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 15,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative pneumatic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by flexures attached to the actuator.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. The actuator is mounted to the pivot shaft by precision ball bearing assemblies within a bearing housing. The actuator supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member. These magnets are typically mounted to pole pieces which are held in positions vertically spaced from another by spacers at each of their ends.
On the side of the actuator bearing housing opposite to the coil, the actuator assembly has typically included a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. These actuator arms extend between the discs, where they support the head assemblies at their desired positions adjacent the disc surfaces. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator bearing housing rotates, the heads are moved generally radially across the data tracks of the discs along an arcuate path.
As explained above, the actuator assembly typically includes an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. The function of the pivot mechanism is crucial in meeting performance requirements associated with the positioning of the actuator assembly. A typical pivot mechanism takes the form of a bearing cartridge having upper and lower bearings with a stationary shaft attached to an inner race and a sleeve attached to an outer race. The sleeve has typically been secured within a bore in the actuator body using a set screw, a C-clip, a tolerance ring or press-fitting, while the stationary shaft typically is attached to both the base deck and the top cover of the disc drive.
Recently, advances in storage technology have greatly increased the data storage capacity of magnetic storage discs. As a result, a single storage disc is now capable of storing large amounts of data which would have required a stack of several discs in the past. Some drive manufacturers have begun to produce disc drives having fewer discs, and even a single disc, as often a single disc may have storage capacity sufficient for a given application. One advantage to providing only one disc is that the actuator must carry only one or at most two heads. Such an actuator may have only one arm and therefore have a rotational inertia much smaller than that of conventional actuators with multiple arms. Moreover, an actuator with only one arm may be produced from a single planar sheet of material, supporting a coil at one end and a head suspension at another. This type of actuator may be more easily manufactured than conventional actuators, and is further advantageous in that it has relatively low inertia, allowing faster seek acceleration/deceleration and having a relatively high natural resonant frequency.
However, a planar actuator does not have the elongate bore a conventional actuator uses to mount a conventional bearing cartridge. While the conventional actuator bearing cartridge has been found to be generally satisfactory when combined with an actuator used to access a large number of discs, this pivot structure also has several disadvantages. For example, the actuator bore wall must be of sufficient height and thickness to securely mount to the cartridge, increasing the rotational inertia of the actuator assembly. Installation of the cartridge into the bore is complicated, generally requiring additional fasteners and/or precision press-fitting operations. Moreover, the conventional actuator/bearing cartridge assembly uses the bearing shaft as the stationary component, while the outer portions of the bearings and the cartridge sleeve rotate around the shaft, adding to the rotational inertia of the assembly.
What the prior art has been lacking is an actuator and pivot assembly which is particularly suited for use with disc drives having two or fewer discs and a planar actuator, which is easily assembled and which has decreased rotational inertia so as to increase responsiveness and raise the resonance frequency of the assembly.
The present invention is directed to an easily assembled bearing cartridge mounting arrangement. In a preferred embodiment, a pivot assembly includes a bearing and a shaft. The bearing is mounted to a disc drive base, and the shaft pivots within the bearing. An actuator is mounted to an upper end of the shaft. Additional features and benefits will become apparent upon a review of the attached figures and the accompanying description.